We present a device for stretching cells adhering to elastic membranes in equiaxial or uniaxial mode, meanwhile allowing real-time imaging of molecular dynamics of live cells at high resolution on an inverted microscope during the entire process of the stretch. We obtained high-resolution images of stress fibers at each stage of the stretch, and found that stress fibers were shortened after one stretching cycle. We, for the first time, captured real-time images of the process of stress fiber disassembly during stretching. Several adjacent stress fibers appeared to reassemble into a single one after stretching. All these indicated that mechanical stretching played important roles in the rearrangement of actin filaments. This device will be especially useful in studies of the molecular dynamics in the process of mechanotransduction. The device is fabricated on a glass slide through a simple procedure and is adaptable to most ordinary laboratories.